Government agencies in Europe have established various requirements for vehicles that travel over the road. Some of these requirements cover agricultural harvesters. One such regulation establishes a maximum width for an agricultural harvester that is operated on public roads.
Most agricultural harvesters are operated on public roads as they go to and from the fields that they harvest. Many of these harvesters are very wide particularly those that are configured to thresh, separate, and clean grain. In order to accommodate the various threshing, separating, and cleaning elements their wheels must be spaced relatively widely apart.
At least two of their wheels must be turned left or right in order to steer the vehicle through the field and over the road. Whenever the wheels turn left and right about their pivot point, the rotation causes a portion of the wheels to move inward toward the side of the vehicle and a portion of the wheel to move outward away from the side of the vehicle.
The portion of the wheel that moves inward toward the side of the vehicle can only do so if there is a space provided between the wheel and the side of the vehicle. The less space there is between the wheel on the side of the vehicle, the smaller the angle through which the wheel can turn before it gets the side of the vehicle.
Wheel interference with a side of the vehicle is not a problem for vehicles such as automobiles. Automobile engines and engine compartments are relatively narrow, and therefore a significant empty space can be provided on the inside of the front wheels of a car to permit the front wheels to turn without rubbing against the engine compartment.
For agricultural harvesters, however, providing this additional space between the body of the harvester and the wheels reduces the space available for productive equipment inside the harvester for threshing, separating, and cleaning the grain.
Attempts have been made to provide a wider harvester body while still providing a good turning angle for the wheels by, for example, supporting the wheels on an angled pivot pin or “kingpin”. As the wheels in these arrangements are turned, the wheels also turn slightly underneath the combine, and avoid rubbing up against the side walls of the combine.
Another system for providing room for a wider harvester body has been to reduce the diameter or width of the tires mounted on the wheels. If the wheels are smaller in diameter, they can be turned farther before they interfere with the side of the harvester body. With a smaller wheel, the harvester body can be made wider.
Neither of these two arrangements have been wholly successful. An angled kingpin will provide a little additional space but that is all. Wheels and tires can be made smaller, but they also require a reduction in the weight (and hence the production capacity) of the combine, which defeats the purpose of making the combine wider to begin with.
What is needed, therefore, is a different arrangement of the steering axle (typically the rear axle) of an agricultural combine that will provide for greater agricultural harvester width and productivity.
It is an object of this invention to provide such a combine rear axle arrangement.